Sceql (seckel): slow and clean esoteric queue language

The program has access to a queue of bytes. The queue initially contains 
a single zero byte.

Instructions:

= NEXT   Dequeue a byte and enqueue it again
- DEC    Decrement the byte that would be dequeued next (wrapping)
_ INC    Increment the byte that would be dequeued next (wrapping)
\ BEGIN  Skip to the instruction after the corresponding END if the byte
         that would be dequeued next is zero
/ END    Go back to the corresponding BEGIN
! GROW   Enqueue a new zero byte
& INPUT  Read a byte from stdin and enqueue it (0 for EOF)
* OUTPUT Dequeue a byte, write it to stdout, and enqueue it again
